The objective of the research proposal is the study of gastrointestinal helminthiasis using Nematospiroides dubius in the mouse as a model. This model will be utilized to determine (1) the nature and role of humoral and cell-mediated immune reactions in the protection phases; (2) the effect of gastrointestinal helminthiasis on the local and system response to heterologous antigens; (3) the effect of genetic factors on the host response to this nematode; and (4) the role of T-and B-cells of the development of acquired resistance.